Conventionally, in multi-carrier radio communications using a plurality of subcarriers, a mobile station sends, prior to data transmission, a request for permission to transmit data, by using a contention channel to the base station, and acquires a subcarrier after receiving permission. As to the contention channels, some schemes are proposed for avoiding collisions of pieces of contention data sent from a plurality of mobile stations, including a scheme that assigns time slots to individual mobile stations, and a scheme that divides the contention data into preamble and message sections, such that a mobile station sends the message section after having confirmed radio resource availability by receiving ACK/NACK etc. as a response to the preamble section (W-CDMA scheme). Such a scheme is disclosed in Non-Patent document 1, for example.
Also, Patent Document 1 discloses a scheme for avoiding collisions of pieces of contention data sent from a plurality of mobile stations, which divides data messages for every OFDM tone, and also assigns time slots for reception.
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-211189.
Non-Patent Document 1: “W-CDMA Mobile Communications System” supervised by Keiji Tachikawa and published by Maruzen Company, Limited, June 2001, pp. 130-134. In Non-Patent Document 1, dividing the contention data into preamble and message sections requires complicated control, and thus requires complicated device configuration.
The technique of Patent Document 1 also requires complicated control in order to separately manage the time slots so as to avoid collisions of contention channels, and thus also requires complicated device configuration